Investigating the Influence of Underground Ore Productions on the Overall Stability of an Existing Open Pit

In the evolution of mining operations that exploit extensive orebodies to depth there inevitably comes a time where the economics of open pit mining reach their break-even ratio. The consideration of underground operations becomes increasingly important to sustain mine production. This paper describes the process of investigation into the influence of full scale underground operations, using three dimensional finite element analysis, to forecast possible pit failure. The numerical analysis was undertaken using data collected at the Prominent Hill mine in South Australia. Analysis was conducted across the range of excavation steps undertaken within the underground mining operation. This full-stage analysis provides predictive information on stability of the open pit in terms of rock/slope failure. The output provides benefits in safety and production and gives operators and regulators much needed data across the mine life to closure.